|Yayınlanma numarası||US9479217 B1|
|Başvuru numarası||US 14/811,804|
|Yayın tarihi||25 Eki 2016|
|Dosya kabul tarihi||28 Tem 2015|
|Rüçhan tarihi||28 Tem 2015|
|Şu şekilde de yayınlandı:||WO2017069821A1|
|Yayınlanma numarası||14811804, 811804, US 9479217 B1, US 9479217B1, US-B1-9479217, US9479217 B1, US9479217B1|
|Buluş Sahipleri||John David Terry|
|Orijinal Hak Sahibi||John David Terry|
|Alıntıyı Dışa Aktar||BiBTeX, EndNote, RefMan|
|Patent Atıfları (25), Referans veren: (2), Sınıflandırma (8)|
|Dış Bağlantılar: USPTO, USPTO Tahsisi, Espacenet|
This invention was produced in part using funds obtained through a grant from the Army Small Business Innovation Research. Consequently, the federal government has certain rights in this invention.
This invention relates generally to wireless communication systems and embedded wireless systems. In particular, this invention relates to embedding digital signals and digital information within digital chaos waveforms. The invention also relates to wireless communications system and embedded wireless systems with multiple signal aggregation at the transmitter and multiple detection at the receiver, wherein digital signals and digital information is embedded within multiple digital chaos waveforms. Further, the invention relates to cooperatively networking the digital chaos signals over a wireless transmission.
A wireless communication device in a communication system communicates directly or indirectly with other wireless communication devices. For direct/point-to-point communications, the participating wireless communication devices tune their receivers and transmitters to the same channel(s) and communicate over those channels. For indirect wireless communications, each wireless communication device communicates directly with an associated base station and/or access point via an assigned channel.
Each wireless communication device participating in wireless communications includes a built-in radio transceiver (i.e., transmitter and receiver) or is coupled to an associated radio transceiver. Typically, the transmitter includes one antenna for transmitting radiofrequency (RF) signals, which are received by one or more antennas of the receiver. When the receiver includes two or more antennas, the receiver selects one of antennas to receive the incoming RF signals. This type of wireless communication between a transmitter with one antenna and receiver with one antenna is known as a single-output-single-input (SISO) communication.
Well known communications system provide a range extension on a SISO system by reducing the data rate and, as a result, increase the symbol duration and/or increasing transmit power. However, increasing transmit power can lead to increase interference to other users sharing the network. The preferred method for improved range reception does not lead to decreased network capacity. For popular multicarrier systems such as SISO WLANs, range improvement is achieved by taking an 802.11a/802.11g signal and cutting the symbol rate. Specifically, the 802.11ah is the range extension an amendment of the IEEE 802.11-2007 wireless networking standard. The goal of the amendment is to optimize the rate vs range performance of the specific channelization. One proposed method to achieve range extension is by down sampling the 802.11a/802.11g physical layer into 26 channels. When the symbol clock is divided by 26, each symbol duration becomes 104 μsec and the corresponding rate for each subcarrier becomes 12 kbps. Keeping the other system parameters the same, (e.g. number of data carriers, cyclic prefix percentage, etc.), the bandwidth for a signal is reduced as well the integrated thermal noise power at the receiver. Therefore, for the same transmit power as 802.11a/802.11g, the thermal noise floor is decreased by 10*log 10 (26). This results in a 14 dB “gain” in the sensitivity of the receiver which is equivalent to at least 5 times improvement in the range of an over existing WLAN. What is needed is a communication device, system and method that increases the transmission range of existing WLAN for specific applications without impacting the data rate and adds flexibility to address new markets for high connectivity environments. A suitable invention would improve transmission characteristics of targeted devices without increase in interference of other nearby the wireless systems and devices. Therefore, what is needed is a method for improved range reception that does not lead to decreased network capacity or increased susceptibility to interference of the wireless device.
Generally speaking, transmission systems compliant with the IEEE 802.11a and 802.11g or “802.11a/g” as well as the 802.11n standards achieve their high data transmission rates using Orthogonal Frequency Division Modulation (OFDM) encoded symbols mapped up to a 64 quadrature amplitude modulation (QAM) multi-carrier constellation. In a general sense, the use of OFDM divides the overall system bandwidth into a number of frequency sub-bands or channels, with each frequency sub-band being associated with a respective sub-carrier upon which data may be modulated. Thus, each frequency sub-band of the OFDM system may be viewed as an independent transmission channel within which to send data, thereby increasing the overall throughput or transmission rate of the communication system. Similarly, multi-code spread spectrum system comprised of perfectly orthogonal high-speed chaos spreading codes transporting independent modulated data can be used to increase its overall throughput or transmission rate of the SISO system. The high-speed “spreading signals” belong to the class of signals referred to as Pseudo Noise (PN) or pseudo-random signal. This class of signals possesses good autocorrelation and cross-correlation properties such that different PN sequences are nearly orthogonal to one other. The autocorrelation and cross-correlation properties of these PN sequences allow the original information bearing signal to be spread at the transmitter.
Transmitters used in the wireless communication systems that are compliant with the aforementioned 802.11a/802.11g/802.11n standards as well as other standards such as the 802.16a IEEE Standard, typically perform multi-carrier OFDM symbol encoding (which may include error correction encoding and interleaving), convert the encoded symbols into the time domain using Inverse Fast Fourier Transform (IFFT) techniques, and perform digital to analog conversion and conventional radio frequency (RF) upconversion on the signals. These transmitters then transmit the modulated and upconverted signals after appropriate power amplification to one or more receivers, resulting in a relatively high-speed time domain signal with a high peak-to-average ratio (PAR).
Transmitters used in direct sequence spread spectrum (DSSS) wireless communication systems such as those compliant with commercial telecommunication standards WCDMA and CDMA 2000 perform high-speed spreading of data bits after error correction, interleaving and prior to symbol mapping. Thereafter, the digital signal is converted to analog form and frequency translated using conventional RF upconversion methods. The combined signals for all DSSS signals are appropriately power amplified and transmitted to one or more receivers.
Likewise, the receivers used in the wireless communication systems that are compliant with the aforementioned 802.11a/802.11g/802.11n and 802.16a IEEE standards typically include an RF receiving unit that performs RF downconversion and filtering of the received signals (which may be performed in one or more stages), and a baseband processor unit that processes the OFDM encoded symbols bearing the data of interest. The digital form of each OFDM symbol presented in the frequency domain is recovered after baseband downconverting, conventional analog to digital conversion and Fast Fourier Transformation of the received time domain signal. Whereas receivers used for reception for DSSS must de-spread the high signal after baseband downconverting to restore the original information signal band but yields a processing gain equal to the ratio the high speed signal to information bearing signal. Thereafter, the baseband processor performs demodulation and frequency domain equalization (FEQ) to recover the transmitted symbols, and these symbols are then processed with an appropriate FEC decoder, e.g. a Viterbi decoder, to estimate or determine the most likely identity of the transmitted symbol. The recovered and recognized stream of symbols is then decoded, which may include deinterleaving and error correction using any of a number of known error correction techniques, to produce a set of recovered signals corresponding to the original signals transmitted by the transmitter.
To further increase the number of signals which may be propagated in the communication system and/or to compensate for deleterious effects associated with the various propagation paths, and to thereby improve transmission performance, it is known to use multiple transmission and receive antennas within a wireless transmission system. Such a system is commonly referred to as a multiple-input, multiple-output (MIMO) wireless transmission system and is specifically provided for within the 802.11n IEEE Standard and 3GPP LTE Advanced standard. As is known, the use of MIMO technology produces significant increases in spectral efficiency, throughput and link reliability, and these benefits generally increase as the number of transmission and receive antennas within the MIMO system increases.
In particular, in addition to the frequency channels created when using OFDM, a MIMO channel formed by the various transmit and receive antennas between a particular transmitter and a particular receiver includes a number of independent spatial channels. As is known, a wireless MIMO communication system can provide improved performance (e.g., increased transmission capacity) by utilizing the additional dimensionalities created by these spatial channels for the transmission of additional data. Of course, the spatial channels of a wideband MIMO system may experience different channel conditions (e.g., different fading and multi-path effects) across the overall system bandwidth and may therefore achieve different signal-to-noise ratio (SNRs) at different frequencies (i.e., at the different OFDM frequency sub-bands) of the overall system bandwidth. Consequently, the number of information bits per modulation symbol (i.e., the data rate) that may be transmitted using the different frequency sub-bands of each spatial channel for a particular level of performance may differ from frequency sub-band to frequency sub-band. Whereas DSSS signal occupies the entire channel band, the number of information bits per modulation symbol (i.e., the data rate) that may be transmitted using the different DSSS sequence for each spatial channel for a particular level of performance.
In the MIMO-OFDM communication system using a typical scheme, a high Peak-to-Average Power Ratio (PAPR) may be caused by the multiple carrier modulation. That is, because data are transmitted using multiple carriers in the MIMO-OFDM scheme, the final OFDM signals have amplitude obtained by summing up amplitudes of each carrier. The high PAPR results when the carrier signal phases are added constructively (zero phase difference) or destructively (±180 phase difference). Notably, OFDM signals have a higher peak-to-average ratio (PAPR) often called a peak-to-average power ratio (PAPR) than single-carrier signals do. The reason is that in the time domain, a multicarrier signal is the sum of many narrowband Signals. At some time instances, this sum is large and at other times is small, which means that the peak value of the signal is substantially larger than the average value. Similarly, MIMO-DSSS schemes can have high PAPR for periodic, sequence or binary-valued sequence; however chaos spreading sequences do not exhibit either of these characteristics and therefore have better PAPR performance for SISO and MIMO operations.
The continually increasing reliance on SISO and especially MISO wireless forms of communication creates reliability and privacy problems. Data should be reliably transmitted from a transmitter to a receiver. In particular, the communication should be resistant to noise, interference, and possibly to interception by unintended parties.
In the last few years there has been a rapidly growing interest in ultra-wide bandwidth (UWB) impulse radio (IR) communication systems. These systems make use of ultra-short duration pulses that yield ultra-wide bandwidth signals characterized by extremely low power spectral densities. UWB-IR systems are particularly promising for short-range wireless communications as they combine reduced complexity with low power consumption, low probability of detection (LPD), immunity to multipath fading, and multi-user capabilities. Current UWB-IR communication systems employ pseudo-random noise (PN) coding for channelization purposes and pulse-position modulation (PPM) for encoding the binary information.
Others have proposed a periodic sequences of pulses in the context of chaos-based communication system. Additional work has relied upon the self-synchronizing properties of two chaotic systems. In such a system, data is modulated into pulse trains using variable time delays and is decodable by a coherent receiver having a chaotic generator matched to the generator used in the transmitter. Such system is known in the art as a Chaotic Pulse Position Modulation (CPPM) scheme.
Such chaotic dynamical systems have been proposed to address the problem of communication privacy. Chaotic signals exhibit a broad continuous spectrum and have been studied in connection with spread-spectrum applications. The irregular nature of a chaotic signal makes it difficult to intercept and decode. In many instances a chaotic signal will be indistinguishable from noise and interference to receivers not having knowledge of the chaotic signal used for transmission. In the context of UWB systems the use of non-periodic (chaotic) codes enhances the spread-spectrum characteristics of the system by removing the spectral features of the signal transmitted. This results in a lower probability of interception/detection (LPI/LPD) and possibly less interference towards other users. This makes the chaos-based communication systems attractive.
There remains a need for improved chaotic coding/modulation methods to produce such attractive communication systems. One prior art, U.S. Pat. No. 6,882,689, issued Apr. 15, 2005 to Maggio et al., attempts to improve chaotic coding using pseudo-chaotic coding/modulation method that exploits the symbolic dynamics of a chaotic map at the transmitter to encode data. The method uses symbolic dynamics as “coarse-grained” description of the evolution of a dynamic system. The state space is partitioned and a symbol is associated with each partition. The Maggio invention uses a trajectory of the dynamic system and analyzes it as a symbolic system. A preferred transmitter of the Maggio prior art accepts digital data for coding and the digital data is allocated to symbolic states according to a chaotic map using a shift register to approximate the Bernoulli shift map acting as a convolution code with a number of states equal to the symbolic states defined on the chaotic map. The pseudo-chaotically coded data is converted to analog form and modulated into synchronization frames in a transmitted signal.
The Maggio prior art has limitations in that it uses only one chaos map (e.g., Bernoulli shift map), that is generated based on the data transmitted. By confining the mapping to Bernoulli shift, information that is repeated in each transmission or repeat symbol can be recognized after observing the waveform over an extended period of time. Once compromised, all future data will be detectable and decodable by a hostile system.
Another prior art system that teaches a chaotic coding/modulation method is described in U.S. application Ser. No. 13/190,478 (“the '478 Patent”), which is commonly invented by the present inventor, and incorporated herein by reference in its entirety. The system of the '478 Application teaches a system, device and method for wirelessly transmitting data via a digital chaos spreading sequences. The '478 Application system teaches constructing and storing a digital chaos spread code sequence in a volatile memory in both the transmitter and the receiver. The system of the '478 Application eliminates the need to generate a digital chaos spread code sequence in the receiver. Information corresponding to the chaos spread sequence used to transmit the digital information is received by receiver for identifying which chaos spread code sequence to use to retrieve the coded information. The '478 Application system further eliminates the reliance on the Bernoulli shift map, and therefore teaches a system which is less detectable by a hostile system.
While the system of the '478 Application solves many of the problems in the prior art, the system has limited applicability to SISO systems. The receiver disclosed in the '478 Application detects and processes one data stream for a single user even in the presence of other users or external interference. The '478 Application therefore would not be useful for transmission systems that jointly processes a plurality of signals detected at the receiver. For example, the joint processing of multiple signals allows for increased capacity and also enhanced reception of a MIMO system.
Generally, the most fundamental issue in wireless communication lies in how efficiently and reliably data can be transmitted through a channel. The next generation multimedia mobile communication system, which has been actively researched in recent years, requires a high speed communication system capable of processing and transmitting various forms of information such as images and wireless data, different than an initial communication system providing a voice-based service.
Then according to the prior art, what is needed is a system and method that does not sacrifice data rate in favor of range, provides increased robustness, while improving LPI/LPD. A system and method is further needed that does exhibits the same positive improvements in a system detecting and receiving multiple signals.
The present invention teaches improvements not found in the prior art. In one aspect, the invention teaches a method of cooperatively networking digital chaos signals over a wireless transmission, comprising:
In another aspect, the invention, A method of cooperatively networking digital chaos signals over a wireless transmission, comprising:
In yet another aspect, the invention teaches a method of cooperatively networking digital chaos signals over a wireless transmission, comprising:
In yet another aspect, the invention teaches a system, device and method for wirelessly transmitting a plurality of data using distinct digital chaos spreading sequences for cooperative wirelessly transmitting data. In one aspect, the invention teaches a constructing and storing a plurality of digital chaos spreading code sequences.
In another aspect of the invention the digital chaos waveform is chosen based on the intended application. For example, transmission of extremely low information bitrate within power signal embedded in high bitrate and high power signal require digital chaos spreading code sequences characterized by unity peak autocorrelation, low autocorrelation sidelobes, very low cross-correlation, and very broad spectrum extent with an extremely low spectral density. The particular digital chaos waveform family such as Bernoulli mapping, Chen's system, or Ikeda map as examples.
In another aspect of the invention, a plurality of constructed digital chaos spreading code are stored in a volatile memory.
Within a single group, the volatile memory includes allocations for storing multiple constructed digital chaos spreading sequence of a length N. The digital chaos memory allocations may be partitioned into M number of groups of equal number of N-length digital chaos spreading code subsequences. Users are assigned a group ID indexing the stored memory. The groups may be indexed in a sequential order. The sequential ordering can be a known order, such as formal ordering of natural numbers (e.g., 1, 2, 3, . . . ). However, the ordering does not need to be consecutive. The only requirement for the index number for the current user is that it sequences the pth group of memory locations associated with group id p stored in at both the transmitter and receiver in a manner such as to provide a one-to-one correspondence between selected digital chaos spreading code sequence at the transmitter and detected and recovered index at the receiver.
In yet another aspect, the invention discloses a data payload wherein when pre-ambles are included and when mid-ambles included, they are constructed so that multiple embedded signals can be detected at one or more locations without interference with native performance of each constituent signal. The data payload may be comprised of at least one non-digital chaos encapsulated signal and at least one digital chaos encapsulated signal that is part of a cooperative network protocol. The pre-amble and mid-amble are also constructed by repeating the digital chaos sequence of sign flipping a copy of the digital chaos sequence in the next symbol period.
In still another aspect, the invention teaches a transmitter system including a volatile memory storing a plurality of digital chaos sequence.
In still another aspect, the invention teaches a receiver system including a volatile memory storing a plurality of digital chaos sequence.
In still another aspect, the invention teaches a system for transmitting data using a digital chaos spreading sequence.
In another aspect, the invention discloses a method for embedding control information in pre-ambles and mid-ambles for a network based on relative amplitude over the replication period. The control information is conveyed using a pre-selected digital chaos sequence.
In yet another aspect, the invention teaches a method for selecting a digital chaos waveform for use in a digital chaos spread sequence.
In yet another aspect the invention teaches a method for embedding multiple disparate communication signals within digital chaos communication waveforms originating from a single antenna subsystem. The method according to this aspect can include multiple antenna element for introducing low probability intercept (LPI) and low probability of detection (LPD), reduced peak-to-average ratio (PAPR), and increased network system capacity.
The present invention teaches a system, device and method for wirelessly transmitting an aggregation of data via a multiplicity of a digital chaos spreading sequence. In one aspect, the invention teaches the use of plurality a priori constructed and stored digital chaos spreading code sequences for data aggregation of digital signals and digital information within multiple digital chaos waveforms. In the context of this invention, data aggregation is any method or technique whereby several different data streams—whether for a single user or multiple users—are collected or aggregated and processed together in a single payload at a transmitter or receiver. Examples include, but not limited, multiple chaos spreading sequences assigned to a single user to increase their transmission rate through at least one transmit antenna; a cooperative network scheme whereby all users received within a specified period of time are detected together, forwarded together (i.e., synchronized) as a single augmented payload through at least one transmit antenna.
In another aspect of the invention a plurality of digital chaos waveforms are chosen based on the intended application or operation. For example, a plurality of digital chaos waveforms may be chosen according to characteristics such as unity peak autocorrelation, low autocorrelation sidelobes, very low cross-correlation, and low PAPR at the transmitter to increased capacity by multiple simultaneous detection of digital signal and digital information with multiple digital chaos waveforms.
In another aspect of the invention, a plurality of constructed digital chaos spreading codes are stored in a volatile memory. The constructed digital chaos spreading codes may be stored in the transmitter and in the receiver.
In another aspect of the invention, within a single group, the volatile memory may include distinct groups or memory locations for storing a constructed digital chaos spreading sequence of a length N. The digital chaos spread sequence may be partitioned into M number of groups of digital chaos spreading code subsequences. Users are assigned a group ID indexing the stored memory. The groups may be indexed in a sequential order. The sequential ordering can be a known order, such as formal ordering of natural numbers (e.g., 1, 2, 3, . . . ). However, the ordering does not need to be consecutive. The only requirement for the index number for the current user is that it sequences the pth group of memory locations associated with group id p stored in at both the transmitter and receiver in a manner such as to provide a one-to-one correspondence between selected digital chaos spreading code sequence at the transmitter and detected and recovered index at the receiver.
In still another aspect, the invention discloses a data payload when pre-ambles are included and when mid-ambles included, they are constructed so that multiple embedded signals can be detected at one or more locations without interference with native performance of each constituent signal. The data payload may be comprised of at least one high PAPR signal and at least one other signal that is part of a common network protocol. The pre-amble and mid-amble may also be constructed by repeating the digital chaos sequence of sign flipping a copy of the digital chaos sequence in the next symbol period.
In another aspect, the invention discloses a data payload wherein when pre-ambles are included and when mid-ambles included, they are constructed so that the data payload may be augmented for the inclusion of a signal field and a symbol delimiter within each of aggregated digital signals and digital information within multiple digital chaos waveforms so that the time of arrival of each constituent signal, part of the aggregated digital signals can be identified accurately and reliably. A signal field detailing the operational mode of the receiver containing at least one information of length of the digital signal and digital information of the transmitting data and rate of said. Further, a signal field comprised containing parity information for protection against and detection errors of other information within the signal field.
In still another aspect, the invention teaches a transmitter system with an augmented payload as described above.
In still another aspect, the invention teaches a receiver system with an augmented payload.
In still another aspect, the invention teaches a system for transmitting a multitude of digital signals and digital information with multiple digital chaos waveforms.
In yet another aspect, the invention teaches a system for receiving a multitude of digital signals and digital information with multiple digital chaos waveforms.
In still another aspect, the invention teaches a receiver system capable of detecting each arrival times of the signal with the augmented payload of multitude of digital signals and digital information with multiple digital chaos waveforms
In still another aspect, the invention teaches a receiver system capable of processing each signal field of the multitude of digital signal and digital information with multiple digital chaos waveforms and configuring the remaining receiver subsystem to recover each of digital signal and digital information with multiple digital chaos waveforms.
In yet another aspect, the invention teaches a method for improvement of multi-user detection as described above, wherein the received multitude of digital signals and digital information with multiple digital chaos waveforms undergo a process to separate the aggregated transmitted digital signal and digital information into streams projected on the null space of all users except itself. This partition is performed for each of the identified digital signal and digital information part of the received aggregated transmitted digital signal and digital information prior to processing by the dispreading subsystem.
In yet another aspect the invention teaches a method for aggregating and embedding multiple disparate communication signals within digital chaos communication waveforms originating from a multiple antennas. The antenna elements of the multiple antenna system need not be co-located only they work in cooperation for introducing low probability intercept (LPI) and low probability of detection (LPD), reduced peak-to-average ratio (PAPR), and increased network system capacity.
A more complete understanding of the present invention may be derived by referring to the various embodiments of the invention described in the detailed descriptions and drawings and figures in which like numerals denote like elements, and in which:
The brief description of exemplary embodiments and best mode of the invention herein makes reference to the accompanying drawings and flowcharts. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical and mechanical changes may be made without departing from the spirit and scope of the invention. Thus, the description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not limited to the order presented.
It should be appreciated that the particular implementations shown and described herein are illustrative of the invention and its best mode and are not intended to otherwise limit the scope of the present invention in any way. Indeed, for the sake of brevity; conventional wireless data transmission, transmitter, receivers, modulators, base station, data transmission concepts and other functional aspects of the systems (and components of the individual operating components of the systems) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It also should be noted that many alternative or additional functional relationships or physical connections may be present in a practical electronic transaction or file transmission system.
As will be appreciated by one of ordinary skill in the art, the present invention may be embodied as a method, a data processing system, a device for data processing, and/or a computer program product. Accordingly, the present invention may take the form of an entirely software embodiment, an entirely hardware embodiment, or an embodiment combining aspects of both software and hardware. Furthermore, the present invention may take the form of a computer program product on a computer-readable storage medium having computer-readable program code means embodied in the storage medium. Any suitable computer-readable storage medium may be utilized, including hard disks, CD-ROM, optical storage devices, magnetic storage devices, and/or the like.
To simplify the description of the exemplary embodiment, the invention is described as being able to be used with single-input-single-output (SISO) and multiple receive antenna systems, such as, single-input-multiple-output (SIMO), multiple-input-single-output (MISO), and multiple-input-multiple-output (MIMO) wireless transmission systems. For example, the invention may be used with a SISO DSSS systems and MIMO DSSS systems as well.
It will be also be appreciated that many applications of the present invention could be formulated. For example, the present invention could be used to facilitate any conventional wireless communication medium. Further, it should be appreciated that the network described herein may include any system for exchanging data or transacting business, such as the Internet, an intranet, an extranet, WAN, WLAN, WPAN, HAN, Ad hoc Networks, mobile ad hoc networks (MANET), satellite communications (SATCOM), and/or the like.
The multiple chaos modulated data source signals may then be spatially mapped (e.g., spread over multiple spatial channels) by spatial mapper 110. The spatially mapped multiple chaos modulated data source signals may then be provided to multiple radio frequency oscillators systems 112 a-n prior to transmitting the spatially mapped multiple chaos modulated data source signals over a communications the multiple spatial channels 116 via multiple antennas 114 a-n.
The spatially mapped multiple chaos modulated data source signals may be received by receiver 104 at multiple antennas 118 a-n. The spatially mapped multiple chaos modulated data source signals may be recovered from the channel 116 using multiple radio frequency receiving systems 120 a-n. RF receiver system 120 a-n may recover the summed chaos modulated data source signal from the signal transmitted over channel 116. For example, RF receiver system 120 a-n may recover the summed chaos modulated data source signal from the signal transmitted over channel 116 using any conventional methods for recovering a data signal from a wireless channel as are found in the art. For example, RF receiver system 120 a-n may recover the transmitted signal by down converting the transmitted signal to baseband analog format and converting the baseband analog signal to baseband discrete signal.
Receiver 104 may further include a MIMO equalizer 122 for separating the spatially mapped multiple chaos modulated data source signals produced by the channel. MIMO equalizer 122 may separate the channel signals according to estimates of each channel amplitudes and phases characteristics associated with each path traverse by the spatially mapped modulated data source signal to produce received baseband modulated signals. The received baseband modulated signals may then be chaos demodulated by multiple chaos demodulators 124 a-n according to data source signal channel. The multiple chaos demodulated data source signals may then be decoded by multiple decoders 126 a-n. The multiple decoded chaos demodulated data source signals may then be merged by a signal merger 128 for combining the multiple data source signals into a single merged signal. In one embodiment, the merged signal may be a copy of the data source 101. Receiver 104 may provide the merged signal to a data sink 130.
Splitter 104, encoders 106 a-n, spatial mapper 110, MIMO equalizer 122, decoders 126 a-n, signal merger 128, and RF oscillator systems 112 a-n, RF receiving system 120 a-n may be of conventional construction and operation as is found in the art. The operation and construction of chaos modulators 108 an and demodulators 124 a-n are discussed more fully below.
The multiple chaos modulated data source signals may then be summed at a signal summer 210 prior to being provided to a RF oscillator system 212. Transmitter 202 may then transmit the summed chaos modulated data source signal via an antenna 214. Transmitter 202 may transmit the summed chaos modulated data source signal via a communication channel 216. The chaos modulated data source signal may be received by receiver 104 at antennas 118 a-n. The summed chaos modulated data source signal may be received by multiple RF receiver system 120 a-n. RF receiver system 120 a-n may recover the summed chaos modulated data source signal from the signal transmitted over channel 216, in similar manner as discussed with respect to
In alternate embodiments, receiver 304 may comprise multiple independent receivers where each receiver may include a chaos demodulator 124. Similarly, transmitter 202 may comprise multiple independent transmitters, where each transmitter includes a chaos modulator 208 a-n.
Transmitter 102 receives data source signal 101 and channel encodes the sequence at channel encoder 106. Data source signal 101 may be bits, symbols, or sampled analog waveforms. A chaos spreading code sequence, the construction of which is described below with respect to
In accordance with the present invention, chaos modulator 108 uses the chaos spreading sequence in the generation of a data payload having pre-ambles and mid-ambles. The pre-amble and mid-ambles may be constructed so that multiple embedded signals can be detected at one or more locations without interference with native performance of each constituent signal. The data payload may be comprised of at least one chaos modulated signal and at least one other signal (either chaos modulated or not) signal that is part of a cooperative network protocol. The pre-amble and mid-amble may also be constructed by repeating the digital chaos sequence of sign flipping a copy of the digital chaos sequence in the next extended symbol period.
In one exemplary embodiment, the data payload includes pre-ambles and mid-ambles that may constructed so that the data payload may be augmented for the inclusion of a signal field and a symbol delimiter within each of aggregated digital signals. The augmented data payload may include digital information within multiple digital chaos waveforms so that the time of arrival of each constituent signal, part of the aggregated digital signals can be identified accurately and reliably. A signal field portion instructing the receiver of at least one length information of the digital signal and data rate scheme information for the remaining payload. Further, the signal field may contain parity information for protection against and detection errors of other information within the signal field.
During operation of chaos modulator 108, the data source signal is spread with the chaos spreading sequence stored in chaos sequence memory 606 using, for example, spreader 602. The chaos spreading sequence may be used to in the generation of the pre-amble 608 and the mid-amble 610. The payload generated by chaos modulator 108 may be augmented to include the symbol delimiter 612 and signal field 614 as is described with respect to
During operation, transmitter 102 receives a data source signal at encoder 106 which channel encodes the data source signal. The data source signals may be any information bearing signals such as bits, symbols, or sampled analog waveforms.
A chaos spreading sequence, the construction of which is described below with respect to
The digital chaos sequences stored in chaos sequence memory 606 are constructed according to the digital chaos sequence generation method 800 of
An irregular sampling interval according to the invention may be, for example, determined by modulo counting of a known sequence generator such as Fibonacci numbers, Lucas numbers, Perrin numbers or any pseudo random number generators. For implementation ease with semiconductor technologies for digital system, the amplitudes may be quantized to finite levels based on the maximum allow cross-correlation (½L, where is L is the number of bits used to represent by each sample amplitude) between code sequences. Independent segments of the digital chaos sequences are grouped together to form a vector span for transmitting the information-bearing communication signals or training signals. It is well-known in mathematics that any signal in an n-dimensional subspace can uniquely represented an n-tuple of scalar corresponds to the projection of the signal onto the orthonormal bases of the n-dimensional. The final step of the digital chaos process is to convert the independent digital chaos segments into a group of orthonormal sequences spanning the same subspace as the original segment. This process may be performed using the Gram-Schmidt orthogonalization process.
The chaos sequence memory 606 (and the chaos replica memory 706 of
Once the chaos sequence memory 606 is fully populated with digital chaos spreading sequences, the entire memory 606 may be subjected to Gram-Schmidt processing. The entire memory 606 may be subjected to an orthonormalization process. In alternate embodiments, independent digital chaos segments may be converted into a group of orthonormal sequences spanning the same subspace as the original segment.
A preferred embodiment of the invention for the packet formation is shown in
A super-frame consists of several frames transmitted in succession with 2 ms gap spacing between frames. Each frame to be transmitted consists of a preamble training sequence, mid-amble training sequence, and data payload. The flexibility of frame structure can accommodate a number of other embodiments to specific applications. In this embodiment, sufficient training information is included to securely and reliably.
As is well known, the key to a successful wireless design is to incorporate sufficient training information to recognize the arrival of packets, align symbol boundaries, estimate channel characteristic and correct for frequency offset. In one embodiment of the invention utilizes a header field. The header field comprises a ten symbol preamble and 48 symbol signal field that defines the configuration state for the receiver. The training sequences are modulated using differential chaos shift keying (DCSK) and repeated predetermine number of times; nine times is used in
As previously noted, the present invention addressed problems in traditional MIMO WLAN transmission. Namely, prior art systems such 802.11x compliant system are more susceptible to interference, wireless collisions, and interception by unintended parties. The present invention addresses these problems by providing a system and method for aggregating and embedding multiple information-bearing communication signals within digital chaos communication waveforms occupying the same frequency channel bandwidth transmitted with a multiple antenna system. Digital chaos may be a waveform generated by sampling a chaos signal, where chaos signals are determined by deterministic nonlinear dynamics. Digital chaos sequences generated according to the invention as described below, are used as a spreading sequence in accordance with various embodiments of the invention.
The signal transmitted by transmitter is received by a receiver 104 of
Receiver 104 receives the transmitted signal to recover the embedded data from the signal. It should be noted that there may be two common receiver modes in preferred embodiments. In the first mode, the high speed multiplication with chaos replica memory 706 occurs directly after operation of A/D 704. This embodiment is preferred when a sampled analog waveform is the information-bearing signal. In the second mode, the high speed multiplication with chaos replica memory 706 occurs prior symbol detect 716 and after Doppler Correction 714 and channel estimation 712 operations. This embodiment is best suited when the information-bearing signal, bits or symbols. Either configuration works for the information-bearing signals in the form of bits or symbol. However the second mode has the best performance and the first mode has the lower power consumptions. After despreading the high-speed digital chaos sequence, the receiver operations are typical of those performed by commercially standard receivers for 802.11x, WCDMA, or CDMA 2000, the description of which is omitted for the sake of brevity.
The chaos modulator 108 and demodulator 124 may be implemented as part of a wireless local area network (LAN), wireless persona area network (PAN), wireless home area network (HAN) or metropolitan area network (MAN) system, a cellular telephone system, or another type of radio or microwave frequency system incorporating one-way or two-way communications over a range of distances. The invention may employ various signal modulation and demodulation techniques, such as single-carrier frequency domain equalization (SCFDE), direct sequence spread spectrum (DSSS) or orthogonal frequency division multiplexing (OFDM), for example. However, throughout this description, references are made with respect to a SIMO and MIMO communication systems or a system including a transmitter and receiver merely to facilitate the description of the invention. All the similar components of the wireless channels 711 will also have similar descriptions to each other.
The transmitters of the present invention may transmit different signals from each antenna in transmit antenna array so that each signal is received by the corresponding antenna in a receiving antenna array at the receive side. Various transmitters described herein may transmitted the data source signal as an aggregate signal and received as an aggregation of all the transmit signals, or an aggregation of parts of the signal. All signals are transmitted once and the receiver demodulates the aggregate signal using a replica of the chaos spreading sequence spreading code stored in chaos replica memory at the receiver.
The digital chaos systems and methods of the present invention are suitable for operation in wireless transmissions desiring coordinated transmissions to enhance network capacity. Such systems often require multiple transactions between tightly coordinated nodes or access points. By coordinated, what is meant is that the transmission protocol of each node (receiver) in a network is organized into a relationship with a second receiving node in the network to ensure that subsequent transmissions are efficient according to the requirements of the network. By efficient, what is meant is that the node to node transfer is optimized according to the requirements of the node or the requirements of the transmission medium. In one instance, improving efficiency may include improving the throughput of the network. Coordinated nodes may be such that one node, or a group of nodes may include a transmission protocol that depends on the transmission received from one node in the network or the group of nodes. In the instance where multiple nodes depend on a transmission received, and the transmission protocol of a multiple of nodes may cooperatively communicate to ensure optimization of the network or transmission medium.
In the instance of multiple transmissions, as noted above, multiple transmissions may create increased opportunities for compromised data transmission or collisions of data transmission. In one embodiment of the invention, the coordinated nodes may include knowledge of the transmission protocol one or more of the other nodes in the network. Alternative, the coordination of the transmissions from one node, or a group of nodes, may depend on the transmission received from a node outside the network or group. In another particular embodiment, coordinated nodes or coordinated transmission over a wireless medium may mean that transmission from one node coordinated with another node may occur at the next transmission opportunity (Txop) or within the time specified by a delay and disruption tolerant protocol known at the receiving side.
The digital chaos waveform described herein may be used to secure the data transmissions while improving network throughput. For example, coordinated multi-point transmission and reception over heterogeneous wireless networks comprise a set of disparate transmission points, access points or nodes operating in the same cell (e.g., “group”), overlaps cells, or mutually exclusive cells, simultaneously or in an coordinated fashion. Coordinated multi-point transmission may be used to utilized to increase throughput and service quality in wireless networks, particularly at or near the edge of a given cell in a cellular network or group of nodes, access points or users.
A typical cooperative network that may be used with this invention is the Internet of Things (IoT). The IoT refers to interconnection and autonomous exchange of data among devices which are machines or parts of machines. IoT may typically be used to support, for example, Machine-to-Machine (M2M) communication. M2M is defined as data communication among devices without the need for human interaction. This may be data communication between devices and a server, or device-to-device either directly or over a network. Examples of M2M services include security, tracking, payment, smart grid and remote maintenance/monitoring. Consequently, a coordinated network according to the invention may include the autonomous exchange of data among devices nodes or members of the coordinated network.
As used herein, nodes belonging to a single cell may be described as “members” of a single group. In some instances, to facilitate the coordination of wireless transmission, members may be described as members belonging to one group, or to more than one group. Signals received by a particular member may be further processed according to the signal preamble or mid-amble information.
As used herein, the coordinated multi-point system may be a MIMO system, wherein the members may use multiple antennas at both the transmitter and receiver. The present invention may be also useful “multi-user multiple-input-multiple-output” or “MU-MIMO” systems. As used herein MU-MIMO systems are wireless communication systems in which available antennas are spread over a multitude of independent group members, access points and independent radio terminals, wherein each member has one or multiple antennas. The present invention may also be used with conventional SISO (single input-single output), SIMO (single input-multiple output), MISO (multiple input-single output) systems, or other similar systems as is known in the art.
Group arrangement 1300 further depicts the wireless transmissions that occur when one digital chaos signal is transmitted between members. For example, member A6 may transmit digital chaos signals to member A2, A5 or An; member C1 may transmit digital chaos signals to C8; B3 may transmit digital chaos signals to B1, B4, or B9 depending on how the digital chaos signal is addressed in the digital chaos preamble. In the instance where the digital chaos is received by a multi-group member, the receiving member may transmit the digital chaos signal to the corresponding group member to which the receiving member belongs. This may be true even when the intended group member belongs to a separate overlaps member. By overlaps, what is meant is that more than one group shares at least one group member. In the group arrangement 1300 shown, group A is overlaps with group C, and group A is overlaps with group B.
It should be noted that the digital chaos signals discussed with respect to the embodiments in
In a typical coordinated transmission according to the present invention, group members operate in a coordinated fashion to improve the overall network capacity for all users sharing the wireless medium. By coordinated fashion what may be meant is that signals are processed together to combat the distortive affects of the wireless medium and mutual-interference to improve the detection for all active distinct users data signal. The group members process the extracted distinct user data signals according to membership or non-membership to a particular group. The group member may process the extracted distinct user data signals according to membership or non-membership to a particular group wherein said extracted distinct user data signals not addressed to the receiving side (e.g., receiving member) are aggregated, time aligned, and retransmitted over the wireless medium at the next transmission opportunity (Txop) or time specified by a delay and disruption tolerant protocol known at the receiving side. For example, the delay and disruption tolerant protocol may be such that the network operates effectively over extreme distances such as those encountered in space communications or on an interplanetary scale. On the other hand, where a digital chaos signal is received by a receiving group member to which it is not addressed, the receiving group member may terminate the signal and not forwarded it at all.
In a typical example, using
In some instances, where group members of different groups are in proximity to each other, a receiving group member may receive a first fragment of the received signal, and time delay transmission of the received signal until such time as a second fragment of the received signal is received by the receiving group member.
It should be appreciated by one skilled in art, that the present invention may be utilized in any device that implements the DSSS encoding scheme. The foregoing description has been directed to specific embodiments of this invention. It will be apparent; however, that other variations and modifications may be made to the described embodiments, with the attainment of some or all of their advantages. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the invention.
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